A positive crankcase ventilation (PCV) system for an internal combustion engine is shown in FIG. 1. An internal combustion engine 10 has a crankcase 12 with oil 14 in an oil pan. Oil mist is formed by the crankshaft 16 having connecting rods coupled thereto. An oil mist forms in the crankcase due to oil flying off of rotating components. A small portion of combustion gases in combustion chamber 50 pass by piston 20 into crankcase 12. The blowby gases pick up oil mist. Rather than venting these gases to the atmosphere, they are routed into the combustion chamber to be burned. Crankcase 12 is in fluid communication with a volume above the valvetrain of a cylinder head 24. Engine 10 is a vee engine with two cylinder banks. A PCV valve 26 is provided in one of the banks. A PCV duct 28 couples between PCV valve 26 and intake manifold 44. PCV duct 28 has a port 30 where it couples to intake manifold 44. Fresh air is inducted into engine 10 via an intake duct 40 that has a throttle valve 42 disposed therein. Fresh gases are provided to intake manifold 44 and mix with blowby gases from the PCV duct before entering combustion chamber 50.
Blowby gases are predominantly exhaust gases, which contain approximately 12% water vapor. During cold weather operation, the water vapor can freeze in the PCV system interfering with proper operation. It is known to use heating elements to avoid freezing of the PCV valve, such as described in U.S. Pat. No. 6,546,921. Additionally, the water can freeze in port 30, i.e., the port through which the blowby gases enter into the intake manifold for mixing with the fresh air. Port 30 in FIG. 1 is positioned on the wall of intake manifold 44. To encourage mixing, duct 28 is often extended into manifold 44 so that port 30 is nearer the center of manifold 44. In such a configuration, the flow of the gases is into port 30. When a lot of fresh, cold air flows past the port, the water vapor freezes in the port obstructing the flow.